Polymerization process and catalyst



United States Patent U.S. Cl. 26093.7 6 Claims ABSTRACT OF THE DISCLOSURE Use of benzenediazonium hexafluorophosphate as an adjuvant for the binary polymerization catalyst system containing a complex of the formula TiCl /aAlCl and at least one compound of the formula R,,AlX where R is alkyl, aryl cycloalkyl or combinations thereof having up to 20 carbon atoms, X is a halogen, and n is Q. or 3, results in the production of polymers of l-olefins of 3 to 8 carbon atoms having increased modulus and lower xylenessoluble content.

This invention relates to the polymerization of olefins to form solid polymers. In one aspect it relates to improved catalysts for such a polymerization. In another aspect it relates to a process for producing solid polymers of olefins having high flexural modulus and low xylenessoluble content.

Background of the invention Polymers of alpha-olefins, particularly of propylene, have long been known and numerous procedures have been disclosed for their production. These polymers are characterized by a greater or lesser degree of stereospecificity and the pressure of a certain amount of a crystalline component. Many of the useful properties of these polymers such as ultimate tensile, hardness, range of melting temperature, etc., appear to depend upon the crystallinity of the polymer. Flexural modulus, a property readily measurable by standard procedures, provides a reliable and consistent means for characterizing these polymers. The higher the crystallinity of a polymer, the higher the flexural modulus values are found to be. For a commercially attractive product, flexural modulus values must be high, preferably above 200,000 p.s.i. and more preferably above 225,000 p.s.i. Heretofore it has frequently been necessary to extract amorphous fractions of the polymer in order to provide products having flexural moduli in this range. It is therefore highly desirable to minimize the production of amorphous polymer, as measured for example by the amount of polymer soluble in mixed xylenes.

Summary of the invention According to our invention, we have discovered that 1-olefin polymers can be obtained with increased fiexural modulus and decreased xylenes-soluble content when the polymerization is conducted in the presence of an organometal modified catalyst system formed by admixing (A) an organoaluminum compound of the formula R,,AlX where R is alkyl, cycloalkyl, aryl or combination thereof having up to 20 carbon atoms, X is a halogen and n is 2 or 3, (B) a titanium trichloride-aluminum trichloride complex resulting from the reaction of titanium tetrachloride and aluminum and having the approximate formula TiCl /3A1Cl and (C) benzenediazonium hexafiuorophosphate.

Objects of the invention An object of this invention is to provide an improved process for the production of olefin polymers.

Another object of this invention is to provide a polymerization process in which there is obtained an increase "ice in flexural modulu and a decrease in the xylene-soluble content of the polymer.

A further object of this invention is to provide novel catalyst systems which when employed in a polymerization process results in the improving of flexural modulus and xylenes-solubles of the resulting polymer.

Other aspects, objects and the everal advantages of this invention will be apparent to those skilled in the art upon consideration of this disclosure.

Description of the preferred embodiments The enumeration of alkyl, cycloalkyl and aryl radicals herein in defining the formulas is intended to include the ,various mixed radical such as alkaryl, aralkyl, alkylcycloalkyl, cycloalkylaryl, and the ike.

The compounds represented by the formula R AlX and utilized as component (A) of the catalyst system vare well known in the art. Examples are triethylaluminum, diethylaluminum chloride, ethylaluminum, sesquichloride, and the like. Mixtures of any of the defined components can also be employed in this process.

The titanium chloride-aluminum chloride complex utilized as component B of the catalyst system according to this invention is also well known in the art. It can be formed by reacting titanium tetrachloride with metallic aluminum. The complex can be represented by the formula TiCl /3AlCl The polymerization reaction is carried out either in a mass systemi.e., the liquid propylene acts as reaction medium-or in an inert hydrocarbon diluent, such as a parafiin, cycloparatfin, or aromatic hydrocarbon having up to 20 carbon atoms per molecule. Examples of hydrocarbons that can be used are pentane, hexane, heptane, isooctane, eicosane, cyclohexane, methylcyclopentane, benzene, toluene, naphthalene, anthracene, and the like. Where an inert diluent is used, the volume ratio of diluent to propylene is in the range of 1:1 to 10:1, preferably 3 :1 to 7: 1.

The polymerization is conducted at any suitable temperature, preferably in the range of O to 250 F. and more preferably to 200 F. The pressure is suflicient to maintain the reaction mixture substantially in the liquid phase. The reaction time is in the range of one minute to 75 hours, more frequently 30 minutes to 25 hours.

Although the invention is illustrated by the polymerization of propylene, any aliphatic l-olefin having up to 8 carbon atoms per molecule can be used. Preferably those having 3 to 7 carbon atoms are used, such as propylene, l-butene, 1hexene, 4-methyl-1-pentene, and the like. Mixtures can also be used if desired.

Hydrogen to control the molecular weight of the polymer, in suitable and known concentrations preferably between about 0.08 and 1 mole percent of the propylene calculated as the amount present in the liquid phase, can also be employed. The tough, strong polymers formed by the process of this invention have wide application in contemporary plastics technology as is well known to the art.

The application of the process of this invention is demonstrated by the following example, although it is not intended that the invention be limited thereto.

EXAMPLE In a series of runs, propylene was polymerized in a l-liter, stirred reactor at F. and 300 p.s.i.g. pressure. A total of 250 g. of propylene, 1 liter of hydrogen (equivalent to 0.67 mole percent hydrogen of the polypropylene present in the reaction system), and the amounts indicated of catalysts and adj'uvants were charged to the reactor. Reaction time was 2.5 hours. At the end of the reaction, the polymerization mixture was cooled, the catalysts were killed with methanol, and impurities were extracted from 3 the polymeric material in a conventional manner with methanol. The polymer was then molded for various tests to evaluate its properties. The following table summarizes the results:

Mole ratio B Flexural 'Xylenes Catalyst, modulus, solubles Run R ADQ- BDH TiCl %AlCl wt. percent b p.s.i.X- 0 wt. percent 6 u RnAlX3-,1 was diethylaluminum chloride in all runs. BDH was benzenediazonium hexafiucrophosphate in all runs.

11 Based on propylene. 0 ASTM D790-61 Deter-ruined by placiug 0.95 g. of polymer in a centrifuge tube, adding 95 ml. mixed xylenes, heating for 15 minutes at 285 F., cooling, centrifuging, evaporating the solvent from a 25-ml. aliquot of the supernatant liquid, weighing the residue, and multiplying The above data show both improved fiexural modulus and reduced xylenes solubles by addition of the adjuvant.

Reasonable variations and modifications of this invention can be made, or followed, in view of the foregoing disclosure, without departing from the spirit or scope thereof.

We claim:

1. A catalyst system formed on admixing (A) a compound of the formula R AlX wherein R is alkyl, cycloalkyl, aryl or combinations thereof having up to carbon atoms, X is a halogen and n is 2 or 3, (B) a titanium trichloride-aluminum trichloride complex having the appropriate formula TiCl /aAlCl and (C) benzenediazonium hexafluorophosphate.

2. A catalyst system according to claim 1 formed by admixing diethylaluminum chloride, titanium trichloridealuminum trichloride complex having the approximate formula TiCl /aAlCl and benzenediazonium hexafluorophosphate.

3. A process which comprises polymerizing an aliphatic l-olefin having from 3 to 8 carbon atoms per molecule in the presence of a catalyst which forms on UNITED STATES PATENTS 3,404,139 10/1968 Fukumoto et al. 260-93] JOSEPH L. SCHOFTER, Primary Examiner E. I SMITH, Assistant Examiner US. Cl. X.R.

mixing a compound of the formula R AlX wherein R 29; 26088.2 

